Description

A 75-year-woman with a Duke’s B adenocarcinoma of the caecum underwent a staging CT examination which revealed an oval, 3.6×2.5 cm fluid attenuation mass (18 Hounsfield units) superior to the carina, posterior to the trachea and medial to the oesophagus (figure 1). She had no symptoms relating to the mediastinal mass. Radiologically the lesion was thought to be most in keeping with a bronchogenic cyst. The most likely potential differential diagnoses were considered to be an oesophageal duplication cyst, a metastatic lymph node mass or a primary oesophageal tumour. In order to establish the diagnosis and exclude the possibility of malignancy, the lesion was aspirated under endobronchial ultrasound guidance (figure 2). The aspirate contained tissue fragments composed of fine spindle-shaped Schwann cells and mature ganglion cells. There was no evidence of malignancy. Immunohistochemistry demonstrated that the spindle cells expressed S100 protein but no smooth muscle actin. There was also positive staining for CD56 and synaptophysin. There were no cytokeratin positive cells. These findings revealed the lesion to be a benign neurogenic tumour, most likely a ganglioneuroma.

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Figure 1

Axial CT image obtained following the administration of intravenous contrast medium. The image demonstrates the oval, fluid attenuation, middle mediastinal mass (black asterisk) which abuts the posterior aspect of the trachea (grey arrow) and the medial aspect of the oesophagus (white arrow).

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Figure 2

Endobronchial ultrasound image of the mass prior to aspiration which revealed the lesion to be predominantly solid and echogenic (white asterisk) with a minor peripheral cystic component (white arrows).